Planothidium incuriatum sp. nov. a widely distributed diatom species (Bacillariophyta) and type analysis of Planothidium biporomum Wetzel, Carlos E. Hoffmann, Bart Van De Vijver Lucien Ector, Luc Phytotaxa 2013 2013-10-18 138 1 43 57 C.E.Wetzel, Van de Vijver & Ector C. E. Wetzel, Van de Vijver & Ector 2013 [151,869,151,178] Bacillariophyceae Achnanthaceae Planothidium GBIF Chromista Achnanthales 6 49 Bacillariophyta species incuriatum sp. nov.   Scanning electron microscopy ( Figs 51–61, 80–89): —Rapheless valve: striae composed externally of two to three rows of small rounded areolae ( Figs 51, 60, 61, 80, 86), the middle row being smaller than the two parallel outer rows ( Figs 61, 86). Striae near the axial area often composed of two ( Figs 51, 60), sometimes three ( Figs 61, 86) rows of areolae near the valve mantle. Striae continuing shortly on the valve mantle ( Figs 61, 80). Raphe valve: striae broader than the virgae, composed of three ( Fig. 56) to four ( Figs 83, 88) rows of rounded areolae ( Fig. 89). Striae internally sunken between raised virgae ( Figs 55, 81–82). Areolae internally covered by individual hymenes ( Fig. 55). Proximal external raphe endings expanded ( Figs 53, 56, 83). Distal raphe fissures bent, continuing shortly onto the valve mantle ( Fig. 58). Internally central nodule raised, with proximal raphe endings not enlarged, deflected to opposite sides ( Figs 55, 87). Distal raphe ends terminate internally with inconspicuous helictoglossae ( Fig. 84). Shallow rounded irregular depressions also present in the central and axial area ( Figs 51, 80, 86). Groups of two small rounded poroids located externally in the valve mantle ( Figs 88–89).     Holotype(designated here): — FRANCE. Île de France Region( Yvelines), Magny-les-Hameaux: ‘ Croix au Buis’creek, Yvette Riverbasin ( 48°43'5.016"Nlatitude 2°4'24.494"Elongitude). Leg. Jeanne Rigaut ( GREBE, Groupe de Rechercheet d'Etudes Biologieet Environnement, Lyon, France),  25/04/2012. Holotypedepicted in Fig. 21, deposited at the National Botanic Garden, Meise, Belgium (slide BR-4315).   FIGURES 80–89.  Planothidium incuriatum sp. nov.SEM views. Pardinho River, Rio Grande do Sul, Brazil. BR-4316. Fig. 80. External view of rapheless valve. Note the similar areolae arrangement with the France population. Fig. 81. Internal view of raphe valve. Fig. 82. Internal view of rapheless valve with wide cavum aperture. Fig. 83. External view of raphe valve showing two reduced striae at both sides forming a rectangular central area. Fig. 84. Internal view of raphe valve reduced helictoglossae. Fig. 85. Internal view of rapheless valve apice. Fig. 86. Detail of central area of rapheless valve showing the triseriate striae, irregular rounded depressions along the apical axis and the external unilateral expansion. Fig. 87. Detail of central area of raphe valve. Figs 88–89. Detail of striae in raphe valve usually composed by 3–4 rows of areolae from the rapheless valve. Note the groups of two small areolae located in the valve mantle located at each stria. Scale bars: Figs 80–83 = 5 µm; Figs 86–87 = 4 µm; Figs 84–85, 88–89 = 2 µm.    Paratype(designated here):— BRAZIL. Rio Grande do Sul, Sinimbú, Pardinho Falls(‘ Salto do Pardinho’), Pardinho River, Rio Pardohydrographical basin,  15/01/2004; Leg. C.E. Wetzel, deposited at the National Botanic Garden, Meise, Belgium(slide BR-4316).   Etymology:—From the Latin incúria, meaning lack of care or attention, neglect, carelessness, indifference.  Taxonomic remarks:—Besides the similarities with  Planothidium biporomum,  P. incuriatumis similar to  P. infrequensLange-Bert. & Rumrich in Rumrich et al.(2000: 212)described from the Andes mountain range in Chile(South America). Differences between the two species include the general outline of the apices being more apiculate and a lower stria density (11–13, not 13–15 in 10 µmas in  P. incuriatum) in the rapheless valve of  P. infrequens.  Planothidium incuriatumdiffers from  P. biporomumby having rostrate extremities, while capitate and wider in  P. biporomum,and by having more rows of areolae per stria in the rapheless valve.  Planothidium incuriatumcan also be confounded with  P. frequentissimum[=  Achnanthes lanceolatavar. dubiaf. minutaGrunowin Van Heurck, sensu Krammer & Lange-Bertalot (1991, pl. 44, figs 1–3)] from which it differs by having clearly larger cells, and  Planothidium frequentissimumvar. magnum(Straub) Lange-Bertalot (1999:292)[=  Achnanthes rostratavar. magnaStraub sensu Krammer& Lange- Bertalot (1991, pl. 44, figs 10–14)] which has clearly elliptical outline and smaller dimensions.   Planothidium incuriatumwas also misidentified in the past as  Planothidium rostratumsensu auct. non null. (see Table 1). However the lectotypeof  Achnanthes rostrata Østrup (1902, p. 253, pl. 1, fig. 11) from Thailand( Siam) illustrated by Krammer & Lange-Bertalot (1991, pl. 43, figs 1–4) has clearly smaller dimensions (length 9.3–14.0 µm, width 5.2–6.5), rounded valves with strongly rostrate extremities and a rounded central area in the raphe valve, and hence cannot be considered synonyms nor conspecific populations.  Zimmermann (1919)described  Achnanthes lanceolata(Bréb.) Grunow var. brasiliensisC.Zimm. (1919: 99)from the Inhahúma River, a tributary of the Pacuí River, a major river on the right bank of the São Francisco River in the north of Minas Gerais( Brazil). According to his drawings, the species has a quite similar valve outline compared to  P. incuriatumand also possesses the unilateral expansion in the central area, with slightly radiate striae in the middle valve portion. Based on his drawings, all we can definitely state is that var. brasiliensisbelongs to the genus  Planothidium.Since Zimmermann’s specimens seems to be impossible to locate ( Gomes et al.2012), a proper typification is not possible for the moment. 2012-04-25 GREBE France France 48.71806 Ile de France Region 1 2.0734706 Lyon 6 49 1 holotype 2004-01-15 Leg. C. E. Wetzel & National Botanic Garden & Meise & Belgium Brazil Sinimbu Salto do Pardinho' Pardinho Falls 8 51 1 Rio Grande do Sul paratype